Communication systems play an important role in information and communication technology. Information may be modulated to different forms of electrical signals which may be further transmitted using different types of communication systems.
In a radio signal communication system, information may be modulated to radio signal in different frequencies suitable for transmitting in wired or wireless signal communication systems in certain frequency bands. Signal mixer may be used to transform the signals into radio frequencies which are suitable to be transmitted using radio transmitter. Typically, the transformation involves a conversion of frequencies of the information signal(s) which produce a new electrical signal having a plurality of frequency components, in which only one or a few of the plurality of frequency components may be useful while the others contributes to noise interfering the useful signal or other signal in other frequency bands. It is desirable to suppress these noise signal from being transmitted.